The present invention relates to an improved annular sealing structure or apparatus for sealing across the annulus between two members, such as the annulus surrounding a valve stem and within the packing gland surrounding the valve stem and the annulus within a tubular well string and surrounding the sealing assembly supported therein.
The K. A. Morales U.S. Pat. No. 4,302,020 discloses a toroidal sealing element for sealing between concentric 10 facing cylindrical surfaces. The sealing element is U-shaped in section and includes an actuator ring having a tapered nose which engages within the gap of the sealing element to deflect its arms outward into sealing engagement with the inner and outer sealing surfaces.
The J. E. Brown U.S. Pat. No. 4,184,690 discloses an annular shaft seal which has two legs joined at an outer apex. The legs seal on their end surfaces against the shaft and on their outer surfaces against the cylinder and cap. Fluid passages are provided in the legs to provide pressure equalization across the seal.
The W. K. Priese U.S. Pat. No. 4,513,946 discloses a convoluted seal ring for a butterfly valve with sealing at the top of each convolution.
The T. P. Nicholson U.S. Pat. No. 4,585,238 discloses a seal having a body with diverging legs and with an outer jacket of yieldable low friction material and an inner energizing spring between the legs.
The L. S. Bialkowski U.S. Pat. No. 3,279,806 discloses a U-shaped metal seal with legs having projections for sealing against inner and outer cylindrical sealing surfaces.
None of these references suggests that a seal could be provided in which the sealing element was an annular metal member having an annular arch which tapers from its ends toward its center so that its sealing surface is at its point of minimum thickness.